Studies of stroke in the population of Rochester, Minnesota, have included a study of subarachnoid hemorrhage (SAH) in which it was determined that the average annual incidence rate for SAH increases with age to the oldest age group. There has been no change in the average annual incidence rate over the 30 years of the study. A study of primary intracerebral hemorrhage showed a decreasing average annual incidence rate over the 32 years of the study and showed that 89% of the patients with primary intracerebral hemorrhage had prehemorrhage hypertension. For one portion of the study, it was shown that anticoagulant therapy contributed to an increased incidence rate of intracerebral hemorrhage. A prospective study of asymptomatic carotid bruit continues. Among 284 patients enrolled in the study, 4 have had cerebral infarcts, 3 have had definite TIA's and 4 possible TIA's. Two have died from myocardial infarction. Twenty-five have undergone a major surgical procedure without complication. A study of the outcome of patients who have had carotid transient ischemic attacks and who have had endarterectomy continues. We are also conducting a study of the results of treatment of subarachnoid hemorrhage and comparing the surgical management with the natural history of the disease. Computerized tomography study of stroke includes a statistical analysis of EMI head scan data, a computerized tomographic and radionuclide study of stroke, an analysis of the basal ganglia region by computer techniques and a correlation of EEG examine with CT scan.